Sound diffuser for loudspeaker and loudspeaker incorporating same

ABSTRACT

A sound diffuser unit comprising a plurality of spaced radially arranged, spokelike members which lie in a common plane. The unit is adapted to be supported in front of, or mounted directly on a loudspeaker. In the preferred embodiment, each of the spokelike members has tapered, angularly positioned, sound impinging surfaces which converge toward the loudspeaker cone and come together along a sound wave dividing line so that a portion of the sound emanating from the loudspeaker will impinge on the surfaces and will be deflected in different directions thereby to provide a greater sound dispersion pattern than can normally be obtained from the loudspeaker.

"United States Patent [72] Inventor Richard Owen Young FOREIGN PATENTS 10 ScoviIle Ave, Oak Park, 60304 791,142 9 1935 France 181/31 7 g i No 1969 Primary ExaminerStephenJ.Tomsky Z5 Patented Jam 1971 Attorney-Wallenstein, Spangenberg, Hattis and Strampel [54] SOUND DIFFUSER FOR LOUDSPEAKER AND R IN AME LOUD-SPEAKER Nicol-P0 AT G 5 ABSTRACT: A sound diffuser unit comprising a plurality of l 1 Claims, 18 Drawing Figs.

spaced radlally arranged, spokellke members wh1ch he 1n a [52] U.S.Cl 181/31 Common plane. The unit is adapted to be Supported in f nt [51 Int. Cl G10k 13/00; f or mounted directly on a1oudSpeakel- [n the preferred m- 1/28 bodiment, each of the spokelike members has tapered, angu- [50] Fleld of Search 181/31A. 1 -1 positioned, Sound impinging Surfaces which converge 3 31 toward the loudspeaker cone and come together along a sound wave dividing line so that a portion of the sound [56] References Cited emanating from the loudspeaker will impinge on the surfaces UNITED STATES PATENTS and will be deflected in different directions thereby to provide 2,167,625 8/1939 Albano 181/31 a greater sound dispersion pattern than can normally be ob- 2,8l9,773 1/1958 Lowell 181/31 tained from the loudspeaker.

SOUND DIFFUSER FOR LOUDSIEAKER AND LOUDSPEAKER INCORPORATING SAME This invention relates, generally, to apparatus for dispersing sound emanating from a loudspeaker, and more particularly to sound diffuser units adapted to be supported in front of loudspeakers by separate support means, or by direct attachment to the loudspeaker.

In the development of high fidelity loudspeakers and loudspeaker systems, much effort has been directed to reproducing sounds which, as faithfully as possible, simulate the sounds which were originally produced and recorded. However, despite the greatly improved fidelity response of present loudspeakers their inherent sound dispersion patterns are rather narrow as compared to sound dispersion patterns produced by musical instruments. Generally speaking, sound dispersion patterns of loudspeakers are substantially cone shaped diverging outwardly from the loudspeaker with the loudest sounds being within the periphery of the base of the cone and the diminishing sounds being outside the periphery of the base of the cone. The cone shaped dispersion patterns become more narrow with increasing frequency of sounds so that the high pitch sounds appear to be within narrow beams extending in the direction of the axis of the loudspeaker, a phenomenon called beaming. I

The beaming effect produced by loudspeakers is undesirable in that it causes the listener to sense the direction of the sound, i.e. from where it is coming, rather than giving the feeling that the sound is coming from all directions. Where loud speakers are used in pairs to reproduce stereophonic sound much of the true stereo illusion is destroyed. That is, before a good stereo illusion can exist, it must seem to the listener that the reproduced sound is not coming from any specific direction. If the ear, or the eye and ear together, can pick out the sound source, as for example the loudspeaker cabinet, the stereo illusion is lost or seriously degraded. This problem is compounded by the fact that directionality of sound, i.e. the ease with which one can detect its source, increases with increases in audio frequency.

Prior art devices to decrease the beaming effect of loudspeakers by diffusing the sound into larger dispersion patterns have been used. However, such devices are either relatively complex, and, therefore, expensive, or they substantially decrease the loudspeaker efficiency. One such prior art device is an inverted cone-shaped diffuser which is mounted in front of the loudspeaker, in alignment with the cone thereof. The loudspeaker and the inverted cone-shaped diffuser are positioned to have their axes vertical so that the sound will be directed in a circle around the loudspeaker thereby to fill the listening area with omnidirectional sound. Another type of diffuser device comprises a slot formed in a rigid wall positioned in front of the loudspeaker cone with a substantial portion of the cone area covered. This type of diffuser, however, decreases the efficiency of the loudspeaker because only a small portion of the sounds produced will pass through the slot. Yet another type of diffuser device is an acoustic lens which delays the sound waves coming from the outer peripheral region of the loudspeaker to form a substantially hemispherical sound dispersion pattern. Generally this is the most complex of the diffuser devices.

In accordance with the present invention, sound dispersing or diffusing apparatus is provided which effectively substantially overcomes the beaming effect produced by conventional loudspeakers. The apparatus is relatively simple and inexpensive to manufacture, and can be readily adapted for use with existing loudspeaker installations. The device is usable and ef fective with all types of loudspeakers, including simple and duplex cones, coaxials and triaxials; small horns; dome radiators; planar diaphragm types; and electrostatics.

Briefly, the apparatus of this invention comprises a loudspeaker sound diffuser unit having a plurality of radially arranged, spoke-like members preferably joined together at one of their ends to form a central hub. The unit is adapted to be positioned in front of the movable cone of a loudspeaker with the hub in registry with the center of the cone, and is spaced therefrom a sufficient distance to prevent the cone from mak ing contact with the diffuser unit when the cone is in its full forward position. The radially arranged spoke-like members advantageously cover an area in front of the loudspeaker cone which is only a fractional part of the total area of the base or mouth of the cone. Thus, while the area covered may be as high as one-half that of the base or mouth of the cone, it preferably is less than one-half thereof. Each of the radially arranged spoke-like members includes one, or more, sound wave impinging surfaces. In the preferred embodiment of the invention, the sound wave impinging surfaces comprise a pair of elongated, tapered, or triangularly shaped. surfaces disposed at an angle to one another which converge toward the loudspeaker cone and come together along a sound wave dividing line which faces the loudspeaker cone so that sound waves impinging upon each of the surfaces will be divided and deflected in different directions to increase the dispersion pattern of the sound waves, particularly of the high frequency sound waves.

The radially arranged spoke-like members can take any of several forms in cross section, as for example, ovate or round, in which case the sound wave dividing line is the elongated portion of the member closest the loudspeaker cone, or, they may have a triangular cross section, in which case, as indicated above, the apex formed by the converging sides constitutes the sound wave dividing line. Also, the radially arranged spokelike members may be either the same size ad jacent the hub region of the diffuser unit as they are near their outer ends, or they may be tapered, increasing in cross section outwardly of the hub region.

The diffuser unit of this invention can be readily mounted in front of, or directly on, a loudspeaker in any one of the several ways disclosed hereinafter, it being understood that other methods of mounting the diffuser unit can be effected without departing from the broad aspects of this invention.

The above and other features and advantages of the invention will be more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals throughout the various views of the drawings are intended to designate similar elements or components. In the drawings:

FIG. I is a front elevational view of a loudspeaker with an embodiment of a diffuser unit of this invention mounted thereon;

FIG. 2 is a side view of the loudspeaker and diffuser unit of FIG. 1;

FIG. 3 is a perspective view of one form of a radial member for a diffuser unit of this invention;

FIG. 4 is a perspective view of another form of radial member for a diffuser unit of this invention;

FIG. 5 is a front elevational view of a loudspeaker with another embodiment of the diffuser unit of this invention mounted thereon;

FIG. 5A is a side view of the loudspeaker and diffuser unit of F IG. 5;

FIG. 5B is a perspective view of one of the radial members of the diffuser unit shown in FIGS. 5 and 5A;

FIG. 6 is a front elevational view of a loudspeaker with still another embodiment of the diffuser unit mounted thereon;

FIG. 6A is a side view of the loudspeaker and diffuser unit of FIG. 6;

FIG. 6B is a perspective view of one of the radial members of the diffuser unit shown in FIGS. 6 and 6A;

FIG. 7 is a perspective view of a loudspeaker enclosure having a portion of the grille cloth broken away to expose several embodiments of diffuser units of the present invention mounted in front of the respective loudspeakers within the enclosure;

FIG. 8 is a side view, partly in section, of one arrangement for mounting the diffuser unit and loudspeaker to a mounting board;

FIG. 9 is a side view, partly in section, of another arrangement for mounting the diffuser unit and loudspeaker to a mounting board;

FIG. is a fragmentary side view, partly in section, showing the radial members fastened to the rear of the grille cloth and in front ofthe mouth ofa loudspeaker;

FIG. 10A is a fragmentary side sectional view similar to FIG. 10 but showing the radial members mounted on the front of the grille cloth;

FIG. II is a fragmentary side view, partly in section. showing the radial members mounted to the outside of a loudspeaker mounting board without a grille cloth interposed between the radial members and the mounting board;

FIG. 12 is a perspective view of a loudspeaker with still another embodiment of a diffuser unit of this invention mounted directly to a loudspeaker; and

FIG. 13 is an enlarged fragmentary side view, partly in section, taken along line 13-13 of FIG. 12 showing one way to mount the diffuser unit to a loudspeaker.

Referring, now, to FIGS. 1 and 2 of the drawing, there is shown a loudspeaker 10 having an embodiment of the sound diffuser unit, designated generally by reference numeral 12, mounted thereon. The loudspeaker 10 may be of conventional construction and design, and includes a support frame 14,:1 magnet and coil element 16, and a loudspeaker cone 18. The base or mouth of the cone 18 is resiliently mounted to an annular portion 14a of the support frame 14 in such a manner as to facilitate controllable forward and rearward movement of the cone 18 under the influence of the magnet and coil element l6.

The sound diffuser unit 12, as illustrated, comprises a plurality of spaced apart, radially arranged, triangularly-shaped, spokelike members 22. The members 22 may be fabricated of wood, plastic, metal, or other rigid or semirigid material, and preferably are symmetrically spaced with relation to one another. The members 22 advantageously are joined at their inner ends 22a to form a hub 24 which is positioned in substantial alignment with the central axis of the loudspeaker cone 18. The outer ends 22b of the members 22, as shown, are attached to a mounting ring 26 provided with spaced openings 28 therethrough for receiving screws for securing the unit 12 on the annular portion 140 of the frame 14 of the loudspeaker 10. The screws 30 desirably are of sufficient length to enable the entire assembly to be fastened to a loudspeaker mounting board, not shown. The combined area of the members 22, as represented by the outer, triangularly-shaped surface 22c thereof, advantageously is less than half of the area of the base or mouth 20 of the loudspeaker cone 18.

As shown in FIG. 3, the radial members 22 comprising the sound diffuser unit 12 can take the form of an elongated tapered tetrahedron having a triangular cross section. The tetrahedron has a pair of sound impinging surfaces 22d-22d which converge in the direction of the loudspeaker cone l8 and come together along a sound wave dividing line 22e so that sound waves impinging upon each of the radial members 22 will be divided and directed in different directions substantially to increase the sound wave dispersion pattern of the loudspeaker 10. In the preferred embodiment of this form of the radial members, the angle A defined by the surfaces 22d-22 is approximately 90".

Referring, now, to FIG. 4 there is illustrated another form of radial member. The radial member, designated by reference numeral 32, is shaped like an elongated one having a circular or ovate cross section. The sound wave dividing line of the member 32 is that portion 34 thereof closest to the loudspeaker cone I8.

FIGS. 5, 5A and 5B illustrate an alternate form of the sound diffuser unit of this invention. As shown, the unit 40, as in the case of the unit 12, is mounted in front of a loudspeaker 10. Here, the radial members 42 arearranged substantially as shown in FIGS. 1 and 2. However, each of the radial members 42 areof uniform triangular cross section from the inner end 42a to the outer end 42b thereof, except for a small tapered portion 420 joined to the inner end 420 which forms part of a central hub 44. The tapered portions 42c can be fastened together in any convenient manner, as by gluing, or the like, it being understood that any of the forms of sound diffuser unit shown herein may be molded as a unitary structure. The radial members 42, as in the case of the members 22, have a pair of sound wave impinging surfaces 42d-42d which converge toward the loudspeaker'cone l8 and come together along a sound wave dividing line 42e.

FIGS. 6, 6A and 6B illustrate a diffuser unit 50 wherein the radial members 52 are essentially circular in cross section. The members 52 are of uniform diameter, and are joined at their inner end to a tapered portion 520. The portions 521' advantageously are secured to one another, as before, to form a hub 54. The sound wave dividing line of each of the members 52 is that portion 52e thereof closest to the loudspeaker cone Referring, now, to FIGS. 7 and 8, there is shown a bookshelf type loudspeaker enclosure 60 with a major portion of a grille cloth 62 broken away to show a plurality of loudspeakers each having a sound diffuser unit, such as unit 12, mounted thereon. A pair of smaller loudspeakers 64 and 66, and a larger loudspeaker 68, are shown in the enclosure 60 to illustrate a common combination of large and small loudspeakers. The loudspeakers, with the diffuser units mounted thereon, are secured to a mounting board 70 by means of screws 72-72. As best shown in FIG. 8, the mounting board 70 has an aperture 74 which is of a diameter substantially equal to the diameter of the base or mouth 20 of the loudspeaker cone so that the annular portion 14a and the support ring 26 extend beyond the aperture 74 and can be secured to' the rear of the mounting board 70 by the screws 72.

In FIG. 9, a loudspeaker is fastened directlyto a mounting board 82 by, for example, screws 84-84. However, the diffuser unit 86 has an outside diameter which is the same as, or slightly less than that of the aperture 88 in the board 82, and snugly fits therein where it can be held in place by glue, or the like. In this embodiment of the invention, it is preferred that the mounting boar d 82 have the same thickness as the support ring 90 of the unit 86 so that the unit 86 will not interfere with either the forward movement of the loudspeaker cone 18 of the loudspeaker 80,or the grille cloth FIG. 10 illustrates an arrangement for mounting a diffuser unit to the rear surface of a grille cloth102. Here, the annular support ring is eliminated and only the radial members 104 are used. As shown,the members 104 are secured, as by glue or staples, to'therear of the grille cloth 102 so that they lie within aperture 106 in the mounting board 108 and are in registry with the loudspeaker cone Preferably, the outer ends 104b of theradial members 104 are tapered, or slanted outwardly so that they will conform to the diverging inner wall of the loudspeaker cone 18. This is especially desirable in those instances where the loudspeaker cone has a relatively large forward movement in that it prevents the outer edges of the cone from making contact with the radial members. After the radial members 104 are fastened to the grille cloth 102, the loudspeaker 110 is mounted in the 'usual manner over the aperture 106.

FIG. 10A shows an alternate form of the mounting arrangement of FIG. 10. Here, the radial members I04 are fastened to the front surface of the grille cloth 102 to increase the dispersion pattern of the sound wave from a loudspeaker 1 10, and to serve as an ornamental design on'the front of the enclosure involved. When mounting the radial members 104, as shown in FIG. 10A, the sound wave dividing lines 104e of the members 104 are parallel to the plane of the base or mouth loudspeaker cone, similar to that of the sound wave dividing lines 42e of the diffuser unit 40 shown in FIG. 5A.

In FIG. 11, the radial members are shown to be of a length greater than the radius of the aperture 122 in a mounting board 124, whereby the outer ends l20b thereof extend beyond the periphery of the aperture 122 and are fastened to the mounting board 124 as by gluing. Here, a grille cloth may or may not be used as desired. Also, in the embodiments shown in FIGS. 10, 10A and 11, the inner ends of the radial members may or may not be joined, as desired.

Referring. now. to FIGS. 12 and 13 a loudspeaker 13.0 has a diffuser unit 132 mounted thereto to form an integral structure. In this instance. the diffuser unit 132 has eight radial members 134 which are fastened together at their inner ends 134a. it being understood that less than, or more than. that number of radial members may be used. The outer ends 134!) of the radial members 134 are fastened to the annular mounting flange 136 of the loudspeaker 130 by any suitable means. FIG. 13 illustrates one preferred form of mounting the ends 134b on the flange. As shown, a bracket 140 extends outwardly and rearwardly of each radial member 134. The outer end 140a of the bracket 140 is bent to extend substantially parallel to the plane of the base or mouth of the loudspeaker 130 and is embedded in an annular gasket 142. The manner in which the end 140a of the bracket 140 is secured at the mounting flange may, of course, vary. Thus, for example, the end 140a may be placed behind the gasket 142, in which case an annular inner portion of the gasket may be cut away to accommodate a bracket which extends rearwardly to a lesser degree so as to maintain a suitable distance between the radial members 134 and the loudspeaker cone 18 when the cone is in its full forward position.

While for purposes of illustration preferred forms of the present invention have been described, it should be understood that variations and modifications may be effected therein without departing from the spirit and scope of the novel concepts disclosed and claimed herein.

lclairn:

1. A sound diffuser unit adapted to be supported in front of a loudspeaker, or to be mounted directly on a loudspeaker at the base or mouth thereof, in spaced proximity to the movable cone thereof, said diffuser unit comprising: a plurality of radially arranged, spokelike members to be positioned in front of the movable cone of a loudspeaker with the inner ends thereof spaced axially from and in substantial registry with the center of the movable cone of the loudspeaker, the outer ends of said spokelike members extending to the periphery of the movable cone and being spaced therefrom, said radially arranged, spokelike members including at least one sound wave impinging surface which faces the cone and defines a sound wave dividing line which acts to divide and deflect sound waves emitted by the cone in different directions thereby to increase the dispersion pattern of the sound from the loudspeaker into an area greater than would otherwise be obtained by the loudspeaker without the diffuser unit.

2. The sound diffuser unit of claim 1 wherein said plurality of radially arranged, spokelike members are joined together at their inner ends to form a hub portion which is positioned in substantial registry with the center of the cone of the loudspeaker.

3. The sound diffuser unit of claim 1 wherein said radially arranged. spokelike members cover an area in front of the base or mouth of the loudspeaker cone which is a fractional part of the total area of the base or mouth of the cone.

4. The sound diffuser unit of claim 1 wherein said radially arranged, spokelike members are circular or ovate in cross section.

5. The sound diffuser unit of claim 4 wherein said radially arranged, spokelike members are tapered, diverging outwardly from their inner ends to the outer ends thereof.

6. The sound diffuser unit of claim 1 wherein said radially arranged, spokelike members are triangular in cross section with two sides thereof forming sound wave impinging surfaces which converge to form a sound wave dividing line facing the movable cone of the loudspeaker.

7. The sound diffuser unit of claim 6 wherein the angle between said two sides at their point of convergence is about 8. The sound diffuser unit of claim 6 wherein said radially arranged, spokelike members are tapered, diverging outwardly from their inner ends to the outer ends thereof.

9. The sound diffuser unit of claim 1 including mounting means for supporting the radially arranged, spokelike members in a fixe speaker.

10. The sound diffuser unit of claim 1 wherein the outer ends of the radially arranged, spokelike members are provided with extensions for securing the unit to a loudspeaker.

11. In a loudspeaker connectable to a source of audio frequency electrical signals and including a movable diaphragm controllably energizable in response to audio frequency electrical signals from said source to generate sound waves both in a forward and rearward direction, the improvement comprising: a sound diffuser unit mounted on the loudspeaker, said unit having a plurality of radially arranged, spokelike members positioned in front of the movable diaphragm of the loudspeaker with the inner ends thereof spaced axially from and in substantial registry with the center of the movable diaphragm and the outer ends thereof extending to the periphery of the movable diaphragm and being spaced therefrom, said spokelike members including at least one sound wave impinging surface which faces the movable diaphragm and defines a sound wave dividing line which acts to divide and deflect sound waves emitted by the diaphragm in different directions thereby to increase the dispersion pattern of the sound from the loudspeaker into an area greater than would otherwise be obtained by the loudspeaker in the absence of the diffuser unit.

position in front of and spaced from a loud- 

1. A sound diffuser unit adapted to be supported in front of a loudspeaker, or to be mounted directly on a loudspeaker at the base or mouth thereof, in spaced proximity to the movable cone thereof, said diffuser unit comprising: a plurality of radially arranged, spokelike members to be positioned in front of the movable cone of a loudspeaker with the inner ends thereof spaced axially from and in substantial registry with thE center of the movable cone of the loudspeaker, the outer ends of said spokelike members extending to the periphery of the movable cone and being spaced therefrom, said radially arranged, spokelike members including at least one sound wave impinging surface which faces the cone and defines a sound wave dividing line which acts to divide and deflect sound waves emitted by the cone in different directions thereby to increase the dispersion pattern of the sound from the loudspeaker into an area greater than would otherwise be obtained by the loudspeaker without the diffuser unit.
 2. The sound diffuser unit of claim 1 wherein said plurality of radially arranged, spokelike members are joined together at their inner ends to form a hub portion which is positioned in substantial registry with the center of the cone of the loudspeaker.
 3. The sound diffuser unit of claim 1 wherein said radially arranged, spokelike members cover an area in front of the base or mouth of the loudspeaker cone which is a fractional part of the total area of the base or mouth of the cone.
 4. The sound diffuser unit of claim 1 wherein said radially arranged, spokelike members are circular or ovate in cross section.
 5. The sound diffuser unit of claim 4 wherein said radially arranged, spokelike members are tapered, diverging outwardly from their inner ends to the outer ends thereof.
 6. The sound diffuser unit of claim 1 wherein said radially arranged, spokelike members are triangular in cross section with two sides thereof forming sound wave impinging surfaces which converge to form a sound wave dividing line facing the movable cone of the loudspeaker.
 7. The sound diffuser unit of claim 6 wherein the angle between said two sides at their point of convergence is about 90*.
 8. The sound diffuser unit of claim 6 wherein said radially arranged, spokelike members are tapered, diverging outwardly from their inner ends to the outer ends thereof.
 9. The sound diffuser unit of claim 1 including mounting means for supporting the radially arranged, spokelike members in a fixed position in front of and spaced from a loudspeaker.
 10. The sound diffuser unit of claim 1 wherein the outer ends of the radially arranged, spokelike members are provided with extensions for securing the unit to a loudspeaker.
 11. In a loudspeaker connectable to a source of audio frequency electrical signals and including a movable diaphragm controllably energizable in response to audio frequency electrical signals from said source to generate sound waves both in a forward and rearward direction, the improvement comprising: a sound diffuser unit mounted on the loudspeaker, said unit having a plurality of radially arranged, spokelike members positioned in front of the movable diaphragm of the loudspeaker with the inner ends thereof spaced axially from and in substantial registry with the center of the movable diaphragm and the outer ends thereof extending to the periphery of the movable diaphragm and being spaced therefrom, said spokelike members including at least one sound wave impinging surface which faces the movable diaphragm and defines a sound wave dividing line which acts to divide and deflect sound waves emitted by the diaphragm in different directions thereby to increase the dispersion pattern of the sound from the loudspeaker into an area greater than would otherwise be obtained by the loudspeaker in the absence of the diffuser unit. 